I solved the problem I had a few days ago with the Wave Driver and Pro Tools crashing on exit (it was a corrupted driver), installed a new one from a new download and the problem is gone.
However I get an annoying error message when I launch Pro Tools for the first time after the boot: 6010 "cannot acquire hardware".
After I click OK Pro Tools open and works just fine. It seems that there's some other software in the background (or some setting) that keeps the hardware busy, but there's no other audio app or audio software running in the background (maybe Windows Media Player?, is it possible to uninstall it?), other than Quick Time 6.0 that's necessary for the movie function in Pro Tools (and I have disabled its audio output).
Another user on the Digi web site experiencing the same problem said something about a dual buffering setting in the Winsystem.